Racial/ethnic disparities (hereafter: disparities) in childhood obesity persist and are widening in the U.S., disproportionately affecting Hispanic and non-Hispanic blacks. From 2003-2007, disparities in childhood obesity between Hispanic and non-Hispanic white children increased by 210%. Childhood obesity has been linked to biological, psychosocial, behavioral, social, and environmental factors. Geographic variance in individual obesity risk suggests that environments play an especially important role. To reduce racial or ethnic disparities, we must understand the most salient environmental characteristics and their specific impacts. To date, no empirical multilevel studies have examined the influence of county-, neighborhood- or school-level factors on obesity disparities over time. The goal of this K01 proposal is to support the PI's development as an independently-funded investigator of etiological research regarding environmental influences on childhood obesity disparities. The proposed research will investigate: (1) multilevel influences on population-level childhood obesity disparities over time, focusing on counties, communities and schools; (2) the extent to which trends in physical fitness disparities among children explain changing patterns of obesity disparities; and (3) child behavior-environment interactions that influence these disparities. The study will utilize multiple data sources, each with unique and complementary strengths, including: (i) 2001-2010 student-level data from the California Physical Fitness Test scores of fifth-, seventh-, and ninth-grade public school students with information on their schools, school districts and counties; (ii) community food environment data from a commercial data source; and (iii) U.S. Census data. The PI will: identify novel environmental predictors of childhood obesity disparities; generate knowledge on potentially critical environments and reasons for changes in disparities trends; determine levels of intervention at which disparity reduction programs are most needed; inform policies and interventions tailored to schools and neighborhoods; and uncover mechanisms through which the environment influences high-risk behaviors. This research will inform the next generation of policies and interventions to prevent and reduce childhood obesity in high risk groups, and contribute to the reduction of health disparities later in life. The PI will extend her expertise through a mentored career development plan with four foci: (1) obesity prevention vis-a-vis race/ethnic disparities in diverse schools an communities; (2) dietary and physical activity behaviors; (3) advanced research skills and hands-on experience with multilevel models; and (4) geographic information science. A multidisciplinary team of experienced mentors will provide ongoing consultation and oversee formal training and research activities. This team, with proven success in developing junior scientists, and the exceptional resources of three San Francisco Bay Area universities, will ensure the successful completion of the project. (End of Abstract)